From left to right, this illustration shows the star HD209458, the extrasolar planet named HD209458b, the spectrograph representing the STIS instrument on Hubble, and the resulting spectral signature of sodium. You can see that sodium's spectral signature (the two dark lines in the rainbow spectrum) are in the yellow band of visible light which means sodium can be measured using the STIS instrument.
Click on image for full size
Courtesy of STScI
Hubble Detects the First Extrasolar Planetary Atmosphere!
News story originally written on November 28, 2001
You probably know there are nine planets in our own solar system...but did you know that we know of 76 planets that are outside our own solar system? These planets orbit other stars and are called extrasolar planets. Just yesterday, scientists using the Hubble Space Telescope (HST) announced that they had detected the first atmosphere of a planet outside our own solar system
HD209458b is a Jupiter-like planet that orbits around a star named HD209458. HD209458 is considered a near-by star at about 150 light years away from our solar system. HD209458b is a huge planet (0.7 times the mass of Jupiter) that orbits very, very close to its star.
Scientists used the STIS instrument onboard the Hubble Space Telescope (HST) to detect the atmosphere of HD209458b. The STIS instrument is the Space Telescope Imaging Spectrograph. It provides spectral signatures in the ultraviolet and visible wavelengths.
Specifically, when HD209458b was crossing in front of its star (see the image on this page), the STIS looked at the light from the star as it passed through HD209458b's atmosphere. And so STIS could process a spectral signature from HD209458b's atmosphere. Spectroscopy depends on the fact that different chemical compounds have different spectral signatures. Scientists looked and found the prominent signature of sodium. Scientists only found half the amount of sodium that models predict, but they did find sodium! In the future, scientists will look for many other molecules in the atmospheres of extrasolar planets. There will be future missions specifically designed to look at extrasolar planets (examples are SIM, TPF, NGST).
The HST was not specifically designed for this type of measurement. In fact, the HST was launched before any extrasolar planets were known. So, it is extra impressive that we can look at the atmosphere of a planet that is so far away!
Shop Windows to the Universe Science Store!
Our online store
on science education, classroom activities in The Earth Scientist
specimens, and educational games
You might also be interested in:
The Hubble Space Telescope (HST) was one of the most important exploration tools of the past two decades, and will continue to serve as a great resource well into the new millennium. The HST found numerous...more
It was another exciting and frustrating year for the space science program. It seemed that every step forward led to one backwards. Either way, NASA led the way to a great century of discovery. Unfortunately,...more
The Space Shuttle Discovery lifted off from Kennedy Space Center on October 29th at 2:19 p.m. EST. The weather was great as Discovery took 8 1/2 minutes to reach orbit. This was the United States' 123rd...more
A moon was discovered orbiting the asteroid, Eugenia. This is only the second time in history that a satellite has been seen circling an asteroid. A special mirror allowed scientists to find the moon...more
Will Russia ever put the service module for the International Space Station in space? NASA officials want an answer from the Russian government. The necessary service module is currently waiting to be...more
A coronal mass ejection (CME) happened on the Sun early last month. The material that was thrown out from this explosion passed the ACE spacecraft. The SWICS instrument on ACE has produced a new and very...more
J.S. Maini of the Canadian Forest Service called forests the "heart and lungs of the world." This is because forests filter air and water pollution, absorb carbon dioxide, release oxygen, and maintain...more